Underground pipelines are commonly used as fluid conduits for conveying fuels such as natural gas to residential, commercial and industrial users. Many existing pipelines are composed of sections of cast iron pipe connected by spigot joints, in which an end or "spigot" of one pipe section is interference-fitted into a "bell" or flared end of the next adjoining section, and the cavity between the bell and the spigot is filled with jute and lead for a gas-tight seal.
Over time some of the joints develop leaks due to ground settlement, vibration, yearly temperature cycles, corrosion etc., and must be repaired or replaced. Typically such pipelines are far too small for a person to enter, and as such repairs have conventionally required excavation of the pipeline. This is a costly and time-consuming process.
It is therefore advantageous to be able to effect repairs from inside the pipeline.
An apparatus capable of carrying out pipe repairs from inside a pipe is disclosed in U.S. Pat. No. 4,986,314 to Himmler, which is incorporated herein by reference. A working head provided with a tool holder is rotatably mounted on the front of a self-propelled trolley which can be inserted into a pipeline. A television camera allows the operator to locate damaged areas, and the tool holder can be fitted with the appropriate tool to effect repairs. The working head is rotatable circumferentially, to permit repairs on any part of the pipe wall. However, in this device the trolley is quite large and is provided with a locking device that enables the trolley to support and resist the force of the working head when grinding, cutting etc. inside a pipe, which requires a large cross-sectional body size that commensurately reduces the effective cross-sectional area of the pipeline when the device has been inserted. Accordingly, the device of U.S. Pat. No. 4,986,314 requires that the pipeline be shut down before repairs are undertaken. Moreover, this device will not fit through a typical opening in the pipeline, so the pipe must first be broken before the device can be introduced. These are significant disadvantages in the repair and maintenance of a fuel pipeline, particularly a natural gas pipeline.
The present invention provides a device for repairing pipes internally. The device of the invention is particularly useful for the sealing of spigot joints. The device comprises a body supporting a drill assembly having upper and lower stabilizing arms which, when opened within a pipe, bear against diametrically opposite points of the pipe wall to stabilize the device. The upper arm is provided with a drill head for drilling into the pipe and a sealant nozzle mechanism for injecting a sealant through the drill hole. Preferably the drill assembly is rotationally fixed to the body so that it can be rotated circumferentially within a selected arc to select the attitude of entry of the drill bit. A camera transmits images of the pipe interior to the operator, who can thus locate and repair successive pipe joints without the need for excavating.
The cross-sectional area occupied by the device of the present invention is relatively compact so as not to interfere with the flow of gas, which allows the device to be used within a "live" natural gas pipeline. The hydraulic drill assembly eliminates the need for a bulky, trolley-like structure for stability and to oppose the force of drilling. Mounting the drill head on an arm of the drill assembly provides significant control and precision in positioning the drill, which is important to ensure the effective dispersion of sealant within the pipe joint. These and other advantages will be apparent from the description of the invention which follows.
The present invention thus provides a device for repairing a pipe having a pipe wall, comprising a body and a drill assembly mounted on the body, the drill assembly comprising upper and lower arms, pivotable between a closed position in which the arms occupy a radial area not substantially greater than a diameter of the body and an open position in which the arms bear against substantially opposing points of the pipe wall to stabilize the drill assembly within the pipe, a locating system for locating a portion of the pipe to be repaired, and a rotating member for rotating a tool against the pipe wall when the arms are in the open position.
The present invention further provides a device for repairing a pipe joint, comprising a body and a drill assembly mounted on the body, the drill assembly comprising upper and lower arms pivotable between a closed position in which the arms occupy a radial area not substantially greater than a diameter of the body and an open position in which the arms bear against substantially opposing points of a wall of the pipe to stabilize the drill assembly within the pipe, a drill head for urging a drill against the pipe wall when the arms are in the open position to produce a drill hole, a locating system for locating a portion of the pipe to be repaired, a remotely operated control panel for controlling the device, and a sealant injection mechanism mounted on the upper arm for injecting a sealant into the pipe joint through the drill hole.
The invention further provides a method of repairing a pipe joint from inside a pipe, comprising the steps of inserting into the pipe a device comprising a body having a drill assembly including an actuator and a sealant nozzle mechanism, locating a pipe joint, activating the actuator to urge a drill bit against the pipe and drilling a hole through the pipe, retracting the drill bit from the hole, moving the sealant nozzle mechanism in front of the actuator and activating the actuator to cause the sealant nozzle mechanism to bear against the hole, and injecting sealant into the hole.